A current mirror circuit used generally has the structure indicated in FIG. 2. A current flows as indicated in the figure by connecting a current source I to the diode-connected transistor T.sub.6. Namely, when a base current of the transistors T.sub.6, T.sub.7 is considered as I.sub.B, a current (I-2I.sub.B) flows into the transistors T.sub.6 and T.sub.7.
The circuit explained above has a disadvantage that a current in the mirror side is lowered by 2I.sub.B.
In addition, a collector current of transistor T.sub.7 is varied due to current modulation by the Early effect depending on a collector potential of the mirror side.